Micro LED Structure With AlGaN Layer for Light Extraction
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Solution Overview
Problem
Existing micro light-emitting diode (LED) devices face challenges in achieving efficient light extraction and electrical insulation, particularly due to mismatched refractive indices and potential electrical shorts, which affect their performance and production yield.
Innovation Solution
Incorporating an n-doped AlxGa(1−x)N layer with a refractive index smaller than the n-type GaN layer, along with a transparent top electrode and additional layers to optimize refractive index matching and reduce electrical shorts, enhancing light extraction efficiency and production yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional LED structure with n-type GaN layer and transparent top electrode is used, then the device structure is simple, but light extraction efficiency is low due to refractive index mismatch
Solution Approach 1:
An n-doped AlxGa(1-x)N layer is introduced as an intermediary layer between the n-type GaN layer and the transparent top electrode. This intermediate layer has a refractive index that is lower than the n-type GaN layer, serving as a refractive index transition layer to reduce total internal reflection and improve light extraction efficiency without significantly complicating the manufacturing process.
2Reliability
If the n-type GaN layer thickness is increased to improve electrical insulation, then insulation performance improves, but light extraction efficiency decreases due to increased internal reflection
Solution Approach 1:
The n-doped AlxGa(1-x)N layer acts as a mediator that reduces the refractive index mismatch at the interface between the n-type GaN layer and the transparent top electrode. This allows for optimized light extraction while maintaining adequate electrical insulation through proper thickness design of the n-type GaN layer, as the intermediate layer compensates for the refractive index issue.
Solution Approach 2:
The refractive index parameter is changed by introducing the AlxGa(1-x)N layer with composition parameter x between 0.02 and 1, creating a gradient in refractive index that optimizes light extraction. The thickness of the n-type GaN layer can also be optimized independently to balance insulation and light extraction requirements.
3Area of moving object
If micro LED size is reduced to increase pixel density, then display resolution improves, but manufacturing precision requirements increase
Solution Approach 1:
The micro LED structure is segmented into distinct functional layers (p-type GaN layer, active layer, n-type GaN layer, and n-doped AlxGa(1-x)N layer), each with specific thickness requirements. This segmentation allows for standardized manufacturing processes that can be replicated across multiple micro LEDs, improving manufacturing precision even at reduced sizes.
Solution Approach 2:
By establishing specific parameter ranges for each layer (such as the Al composition x between 0.02 and 1, and minimum thickness of 10 nm for the n-doped AlxGa(1-x)N layer), the patent provides clear fabrication guidelines that maintain manufacturing precision while enabling smaller device sizes for higher pixel density displays.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution improves light extraction efficiency and reduces electrical shorts, resulting in enhanced performance and higher production yield of micro LEDs.
Implementation Method 1
A refractive index of the n-doped AlxGa(1−x)N layer is smaller than a refractive index of the n-type GaN layer
Data Source
AI summary
A micro light-emitting diode device includes a substrate, a micro light-emitting diode, and a transparent top electrode. The micro light-emitting diode is disposed on the substrate and includes a p-type GaN layer, an n-type GaN layer above the p-type GaN layer, an n-doped AlxGa(1−x)N layer above and in contact with the n-type GaN layer, and an active layer between the p-type GaN layer and the n-type GaN layer. x is equal to or greater than 0.02 and smaller than 1. The transparent top electrode covers and is in contact with the n-doped AlxGa(1−x)N layer. A refractive index of the n-doped AlxGa(1−x)N layer is smaller than a refractive index of the n-type GaN layer. A sum of the thicknesses of the n-type GaN layer and the n-doped AlxGa(1−x)N layer is greater than a sum of the thicknesses of the active layer and the p-type GaN layer.